I had a 351 short block in an Xf ute with an XD front end.

The heat was too much, at the lights the temp would climb up, etc.

I actually put one rear facing scoop to get the heat out exactly as you are thinking but this did absolutely nothing...lol

The only thing that worked was big twin thermo fans on a manual switch so I could manually put them on knowing what was coming up in the traffic. This did not reduce the temp but it 100% maintained the temp at whatever degree it was at the time of putting it on.

It saved the engine for sure.

Having saying that it may have been a combination of both large twin thermos along with the rear scoop to exhaust the heat not to mention putting the heater on full blast on 40 degree days in a ute cab...lol.....Those were the days of V8 love....LMAO